1. Field of Invention
The present invention relates to a controlling system and a method for operating the same. More particularly, the present invention relates to a critical dimension controlling system and a method for operating the same.
2. Description of Related Art
In the manufacture of integrated circuit, photolithography process is used to transfer patterns from a photo mask having customized circuit patterns to thin films formed on a wafer. The image transfer process comprises steps of forming a photoresist layer on a non-process layer, illuminating the photoresist layer through a photo mask having the customized circuit patterns, developing the photoresist layer and then etching the non-process layer by using the patterned photoresist layer as a mask. Hence, the image transfer process is accomplished.
However, the critical dimension of the pattern in the photoresist layer is affected by several factors including the exposure dosage, thickness of the photoresist layer and the variables in the development process. Therefore, for the different wafers in the same process procedure of the same product line, the critical dimension of the pattern formed in the material layer by using the patterned photoresist layer could be varied.
For a particular process procedure, a critical dimension control limit range is defined according to the specification of the product line. If the critical dimension of the pattern of the patterned photoresist layer on a wafer is beyond the critical dimension control limit range, the device element formed by using the patterned photoresist layer could behave undesirably and abnormally.